1. Field of the Invention
The present invention relates generally to aligners, placed at the feet of equipment having rotating shafts in order that the axes of shaft rotation may be aligned, and more particularly to an improved aligner that is shimless (i.e., uses no shims), does not require the lifting of the equipment, and does not disturb the previous side alignment and lateral position of the equipment.
2. Description of the Related Art
Shaft alignment is a critical aspect of all mechanical systems utilizing equipment where rotational force is transferred from one piece of equipment to another via shafts that are fixedly coupled, whether by flanges, gears, or other forms of couplings. In a classic structure, one machine is acting as a driver transferring rotational energy to a second machine. The driver machine has a shaft and the driven machine has its own shaft. To efficiently transfer energy and minimize wear to the equipment, the two shafts must be coupled in such a manner that the respective centerlines of the two shafts are inline. In other words, the centerlines must overlap without horizontal offset, vertical offset, angular offset, or multiple offset.
Shaft horizontal offset occurs when the shaft centerlines are parallel on the same horizontal plane and thus require the equipment to simply receive horizontal shifting with respect to each other. Vertical offset occurs when the shaft centerlines are parallel on the same vertical plans and thus require the equipment to simply receive vertical shifting with respect to each other. Angular offset occurs when the shaft centerlines are at an angle to each other. Multiple offset occurs when equipment has components of angular and vertical and/or horizontal offset.
Misalignment of shafts and associated flanges, couplings, bearings, or gears causes noise and vibration, and thus accelerated wear. Misalignment will lead to frequent failures of couplings, bearings, or seals in the rotating machines. The long term effects of misalignment can be made apparent by the resulting binding, fluid leakage, powder, loose bolts, and cracks. These effects make misalignment a costly problem to all rotating shaft machines.
Many rotating shaft machine alignment problems can be traced to design, installation, or deterioration problems with the foundation, base or soleplate, or the machine casings/frames themselves. Thus not only will it be difficult to obtain accurate alignment initially, but it is going to be equally difficult to maintain proper alignment over long periods of time, if the machinery is sitting on unstable or improperly designed foundations and frames.
Even if the machines are satisfactorily designed and produced to minimize shaft alignment imperfections at initial installation, realignment must be repeated over time. Load conditions, heat generation during extensive hours of operation, environmental factors, floor expansions and contractions, and wear can alter the alignment of the shafts.
The shafts rotate on bearing and those bearings wear out and expand or contract according to operating environment conditions and heat generated during operation. While an experienced technician will know to compensate for such thermal growths during cold alignment checks (i.e., before the equipment is started), mistakes in calculations can occur and experience levels differ, thereby often leaving a need for adjustments once the equipment has gone into operation. Thus, the machinery shaft misalignment has to be measured by rotating the shafts of the machines to determine shaft straightness and compensate for the misalignment with reference to their bearings.
In a typical method of fixedly coupling shafts, each shaft has a coupling flange. The flanges are coupled by a coupling spool. Since the shafts rotate on bearings, the most common method of monitoring the misalignment of the shafts is to monitor the rim and face of each rotating flange with respect to the bearings. Technicians in the field have various methods for measuring the amount of misalignment using mechanical dial gauges and manual record keeping or by sophisticated computer equipment. But the important point is that once the amount of pertinent misalignment is known, the entire equipment is slightly repositioned by appropriate horizontal, vertical, and even rotational shifting.
To understand how the equipment is shifted or moved to effectuate shaft realignment, it is necessary to understand the typical means of securing equipment to the floor. It is a common industry practice to anchor bolts into the floor that will match up with the holes in the feet of the equipment. These bolts are referred to as hold-down bolts. When the feet are in position through the hold-down bolts and nuts are tightened over the feet and onto the bolts, the equipment is secure and unmoving even during the vibration of operation. It is at the machine feet and hold-down bolts that shaft misalignments are corrected by appropriate adjustments to the relative positions of the feet.
By merely loosening the retaining bolts, the equipment can be laterally and rotationally shifted on the horizontal plane. That is so because the holes are slightly oversized to allow for some movement of the feet with respect to the hold-down bolts rising from the floor.
However, vertical shifting of the equipment or movement of the feet up or down with respect to each other is a more complicated situation in the known art. The industry standard has been and remains to employ shims. Many devices have been proposed to effectuate vertical shifting of the individual machine feet, including jackscrews, portable hydraulic jacks, wedges, pry bars, cranes, hoists, and sledge hammers. However, precision deficiencies, excessive time required, and danger to machinery and personnel, are known as common disadvantages of such adjustment means. Attempts at improving over those means have been made but have failed in practice. For example, U.S. Pat. No. 3,849,857, issued in 1973 in the name of Murray, acknowledges the prior art limitations and discloses an alignment mechanism making use of a ball bearing table to facilitate vertical alignment without disturbing horizontal alignment.
But, that alignment mechanism like others has not found wide application in the industry, in part because they require significant customization and down-time to adept onto machines in the field. Additionally, many of these improved alignment mechanisms remain unacceptably bulky and therefore unworkable within the tight spaces in which many of these machines are located. Therefore, shims remain the most efficient known means of aligning the feet of machines, previous proposed designs in the art being impractical for cost, safety, or workability issues.
Thus, in the industry, one or more shims are placed under the bottom of each equipment foot until the necessary vertical equipment shifting has occurred to bring the shafts into alignment. In other words, correction of the vertical position of the machine feet is done by adding or subtracting shims of prefabricated thicknesses. There is an entire market of manufactures that sell prefabricated shims of varying shapes, thicknesses, and bolt accommodating slots. Depending on the type of machine feet and hold-down bolt size, appropriate shims are purchased and stacked below each foot of the equipment needing to be vertically shifted.
But there is at least one more important factor in pursuing satisfactory shaft alignment. Aside from having to obtain proper lateral or rotational shifting on the horizontal plane (accomplished by loosening the hold-down bolts and moving the machine) and having to obtain proper vertical shifting of the individual machine feet (commonly accomplished with the industry standard prefabricated shims), it is still necessary to account for phenomenon called “Soft Foot.” A classic example of soft foot—like a bar table with one short leg—occurs when the machine naturally rests on three legs and the fourth leg is short. If not properly corrected before beginning the actual alignment, it may be difficult, even impossible, to achieve acceptable shaft alignment.
The technician may implement the exact machine movements/shifting as required by the alignment calculations the measuring equipment dictates, only to find that, because of soft foot problems, the machine frame distorts when hold-down bolts are tightened. As a result there will be little or no achieved improvement in shaft alignment.
Furthermore, even if soft foot problems do not completely prevent satisfactory horizontal and vertical shifting of the equipment to achieve the necessary shaft alignment, the frame distortion resulting from a soft foot can also lead directly to unnecessary vibration and premature component failure. In fact, soft foot has been observed to increase machine vibration levels by as much as ten times. In such cases, by not recognizing the contribution made by the soft foot, a technician may have tried to lower the vibration levels by better balancing, better alignment and so on, but yet obtained very little improvement. See, e.g., Buscarello, R. T., Practical Solutions to Machinery and Maintenance Vibration Problems, 99-105 (1979).
Soft foot is thus an issue that is integral to obtaining proper shaft alignment and even if shaft alignment is not needed, soft foot can also be destructive of the equipment if left uncorrected. There are different types of soft foot. In its simplest form, a foot can either be parallel or bent. It is relatively simple to locate and correct for a parallel foot. In the situation of parallel foot, the foot remains parallel to the supporting foundation but simply remains shorter than it should be. The current common industry practice would be to add the necessary stack of prefabricated shims under that foot.
It is substantially more complex to determine the profile of and correct for a phenomenon called “Bent Foot.” In a bent foot situation the foot of the machine is either slightly bent up or down relative to the foundation. The bottom of the bent foot forms an angle to the foundation. The degree of bending is relative because the discrepancy between the foot and the foundation can be due to problems with the foot itself, the base-plate the foot sits on, and/or with the foundation. Furthermore, even if there are no design faults in the base-plate upon which the foots rests, the foundation, or the foot, a soft foot problem may still exist in the form of induced soft foot (also called piping strain) because external forces, like pipe and conduit stress, coupling misalignment, etc., cause the foot to move away from the base.
Regardless of what causes the bent foot situation, it must be corrected. Unlike the simpler parallel foot problem, where the industry standard is to use a stack of prefabricated shims of uniform thickness to correct the problem, bent foot can not be resolved that easily. Instead it will be necessary to measure the size and the shape of the gap between the foot and the foundation. Because the foot is at an angle relative to the supporting foundation, a uniform thickness shim will be unable to solve bent foot. Instead, in the case of a bent foot, the technician will need to create a custom “taper shim” to completely fill the gap. Basically, gap measurements need to be taken at all sides of the foot to custom build a shim with thicknesses at each side to match the gaps. In effect the “taper shim” when placed under the bent foot will create a new lower surface that is perfectly parallel and in complete contact with the foundation base. In most instances the “taper shim” will a tapered structure to complement the bent foot angle.
This state of the art in machine alignment, with all its known problems, leads up to the present invention. To date, placement of appropriate shim packs under the individual feet of the machine remains the industry standard for shifting the machine to achieve appropriate shaft alignment. This process requires shut down of the equipment to loosen their hold-down bolts, and then raising the equipment by mechanical or hydraulic means to enable removing or adding the required shims. This process of vertical shifting disturbs the equipment side alignment and distance between machine to machine shaft couplings, which results in additional equipment downtime and production and man-hour losses.
In heavy industrial applications the cost of downtown can exceed $10,000 per hour, so the tedious and time consuming process of adding and subtracting shims can be quite costly. Also, additional equipment is generally necessary to assist in shifting the machine while shims are added or subtracted. Therefore, shims to accomplish alignment of the machine shafts have left an unresolved need for a more efficient mechanism.
While wedges, jackscrews, hydraulic jacks, cranes, hoists, and even more brute means like sledge hammers are known to be able to achieve some level of vertical and horizontal machine shifting at the feet, none have been able to present a solution that efficiently, safely, and cost effectively achieves shaft alignment even while simultaneously accommodating the “taper shims” necessary to correct for bent foot.
For example, U.S. Pat. No. 2,170,690, issued in the name of Mafera, discloses the use of wedges as a means of accomplishing vertical shifting of individual machine feet. In that disclosure, two wedge members are basically allowed to slide against each other on their hypotenuse side. The bottoms of the wedge members are to remain parallel to each other throughout the sliding motion and accomplish vertical shifting of the machine, given that the co-acting wedge members are placed in between the machine and the foundation. However, that wedge invention also teaches that the wedges should have aligned slots and that the wedges should attach to an aligner base that has a countersunk slot. In this manner the invention allows the hold-down bolt freedom to slide along the countersunk slot and thereby allows the machine to shift horizontally. In that patent, it is expressly taught that these design features of leaving the wedge members free to rotate is a critical component of the aligner mechanism. As will be explained, such approach solves some problems but creates new more critical complications.
In particular, such prior art wedge designs are deficient because it leaves unresolved the problem of bent foot. For if a “taper shim” has been placed under the machine at a particular bent foot, and later such prior art wedge mechanism is added, the fact that the wedges are free to rotate will effectively defeated the purpose of the taper shim. In other words, a machine foot forms a unique gap shape relative to the foundation. The taper shim is supposed to match that gap perfectly and any rotational movement of the taper shim, due to the rotational freedom of the wedges, defeated the goal of matching the gap.
The wedge designs like those in U.S. Pat. No. 2,170,690 are also deficient because in giving the hold-down bolt freedom to slide along a counter sunk slot in the aligner mechanism base, efficiency in placement of the aligner mechanism is lost. Implementation of that wedge-based aligner mechanism in the field means that additional hold-down bolts have to be adapted (i.e., drilled) into the foundation. Furthermore, because in the field there is often limited access or hot-work restriction, it is often difficult to add such prior art aligner mechanism designs to the machines already in operation in the field. Thus, the known wedge designs are difficult to install in the field.
On a commercial level, the inventors know of no aligner mechanism that is in actual production and use. So while some patent applications on the subject may exist, the only commercially implemented method of alignment at present remains the use of shims—creating an entire market of precut shims manufactured in a variety of sizes. It is a likely reflection of the non-viability of prior art aligners that has left manufactured precut shims the industry standard for accomplishing equipment alignment.
Therefore, there remains an unresolved need for an aligner mechanism that can replace the industry standard prefabricated shims, replace the need for external lifting mechanisms, can be efficiently and safely added unto machines already in the field, safely allows for alignment without having to shut-down the machines, accomplishes vertical alignment of the feet without disturbing horizontal alignment, and accomplish vertical and horizontal alignment without disturbing existing “taper shims” that are under the feet to correct bent foot.